Plackett-Burman and Box-Wilson designs for the removal of mercury (II) by cypress pines and leaves, optimizing the surrounding conditions

Abstract

In this study, the removal of Hg (II) from cypress leaves and cypress pines was examined. Factors like time of contact (1–60 min), amount of biosorbent used (0.02–0.06 min), pH levels (1.2–6.52 min), initial metal concentration (100–250 ppm) temperature (20–40 min), strength of ions (0.5–1.5 M), and speed of stirring (0–250 min) were studied. Kinetic data were described using both pseudo-first-order and pseudo-second-order models. Equilibrium data were analyzed using Langmuir and Freundlich models, with the Langmuir model fitting the data best. The kinetic data were best described by the pseudo-second-order model. Thermodynamic studies showed that the removal of Hg(II) by cypress leaves was exothermic. The Plackett–Burman design (PBD) and Box–Wilson designs were used for optimization, recommending values of 250 mg/L, 5.98, 7.98 min, and 0.5 g for the variables Co (initial concentration of Hg(II) ions), pH (acidity level), contact time, and mass of KNO3 (potassium nitrate) for the removal of mercury (II) by cypress pines.